Generally, the telescope imaging system is adopted and applied to investigating objects in a long distance for scientific applications including biological and astronomical observations. The telescope imaging system is mainly classified into a refractive telescope imaging system, a reflective telescope imaging system and a catadioptric telescope imaging system. For the refractive telescope system, there is a single convex lens accompanying an achromate and disposed at the front end of the observation tube thereof for the receipt and refraction of the parallel beam from the object in a long distant, the image of which is formed at the focus of the single convex lens, wherein the focus is located at a position between another convex lens and a focus thereof, wherein the another convex lens serves as an object lens and is located at the rear end of the observation tube. Accordingly, the image of the distant object is magnified and observed by the observer or an image recording device.
Currently, the Newtonian reflective telescope system dominates in the various types of the reflective telescope imaging system. The Newtonian reflective telescope system mainly comprises a secondary planar mirror and a primary concave reflective lens formed by a spherical surface or paraboloid surface coated with a reflective matter, wherein the secondary planar mirror is disposed before the focus of the primary concave reflective lens and inclines at an angle of 45 degrees at the front end of the observation tube corresponding to the longitudinal axis thereof. Accordingly, when the parallel beam from the object in the long distance enters the observation tube, the parallel beam passes through a pathway bending at a right angle after being reflected to the planar subordinate mirror by the primary concave reflective lens for being focused as an image outside of the observation tube.
A basic derivative of the catadioptric telescope imaging system is the Schmidt type, which basically comprises a primary spherical mirror and a correction lens in the observation tube thereof, so that the parallel beam from a distant object is first refracted by the correction lens and focused as an image by the primary spherical mirror thereafter. An advanced derivative of the catadioptric telescope imaging system is the Cassegrain type, which is distinguished from the Schmidt type in that the primary mirror further has an opening, so that the beam from the object is reflected to the subordinate mirror by the primary mirror and passes through the opening for being focused as an image at an rear end of the observation tube. Based on the abovementioned, the telescope imaging systems of the prior art is designed for the parallel beam of the object in the long distance, whereas they fail for a clear image of the spot light of the object in a short distance.
In order to overcome the drawbacks in the prior art, a catadioptric telescope imaging system is proposed through arduous experiments and research.